Pain abatement research is a major area of study which goes hand-in-hand with pain research itself. In many cases pain is a symptom of an underlying malady or trauma so the presence and nature of the pain in these cases is sometimes essential in aiding awareness and the diagnosis of the underlying illness. The abatement of pain has traditionally been effected using various external and internal treatments. Examples of external treatment include acupuncture, electro-shock treatment using transcutaneous electrical nerve stimulation (TENS), use of temperature such as application of hot or cold packs or topical application of cooling or heating formulations. Examples of internal, invasive treatments include drug treatments by oral administration or injection of freezing agents. Where feasible, the external physical methods of alleviating pain are preferable over the invasive, internal techniques for obvious reasons.
The application of hot or cold to localized pain such as muscle or tendon pain to reduce swelling has a long history. There are many devices for heating or cooling parts of the body. Hot water bottles and ice or cold packs are among the oldest and simplest devices for applying heat and cooling respectively. Another type of device is the heating blanket that uses electrical resistive heaters for heating. U.S. Pat. No. 4,094,357 discloses a heat transfer blanket which uses heat pipes coupled to heating/cooling systems. U.S. Pat. No. 5,269,369 teaches a body suit which utilizes a system of heat pipes to redistribute body heat for heating or cooling the person wearing the suit.
U.S. Pat. No. 4,459,468 issued to Bailey discloses a temperature control fluid circulating system provided with a thermal blanket and a large refrigerant reservoir using thermoelectric units inserted directly into the reservoir to heat and cool the refrigerant in the reservoir. U.S. Pat. No. 3,154,926 issued to Hirschhorn teaches a cooling blanket with a coolant reservoir with substantially all of one side of the reservoir in contact with thermoelectric Peltier units to cool the liquid in the reservoir. U.S. Pat. No. 4,523,594 issued to Kuznetz discloses a heat exchange jacket that can be used in an open loop mode or a closed loop mode. In the open loop mode the jacket is connected to a hot or cold water faucet in a hospital or home while in the closed loop mode a thermoelectric device is used to heat/cool water in the reservoir which is in series with a pump. Similarly, U.S. Pat. No. 3,967,627 issued to Brown is directed to a hot/cold applicator system utilizing a peristaltic pump in series with a patient blanket, a fluid reservoir and a heat exchanger for heating/cooling the fluid. A drawback to these types of devices is poor efficiency of cooling the refrigerant since essentially the entire volume of coolant contained in the reservoir must be cooled.
U.S. Pat. Nos. 4,962,761 to Golden and 5,174,285 to Fontenot disclose fluid circulation systems for use with thermal bandages, pads or blankets. These devices provide a thermal blanket with closed loop fluid circulation systems with fluid module housings which are in thermal contact with heating/cooling devices. A drawback to these types of devices is poor cooling efficiency for cooling the refrigerant since the latter contacts the cooling devices indirectly through the walls of the fluid modules.
U.S. Pat. No. 3,888,259 issued to Miley discloses hypothermia device for therapeutic applications. The device includes a fluid pump located between a heat exchanger and a reservoir and a double impeller pump with an upper impeller connected in series with the reservoir and the hot side of a thermoelectric unit and a lower impeller pump connected in series with the cold side of the thermoelectric unit and the patient blanket. Once water fills the system during operation of the pumps a quasi closed-loop is set up for the cooling water circulated between the blanket, the second set of impellers and the cooled side of the thermoelectric unit. A drawback to this system is the need for two pumps to sustain the pumping action in the two circulation systems.
U.S. Pat. No. 4,170,998 to Sauder is directed to a portable cooling apparatus for cooling a limb of a patient which includes a compressor and evaporator for condensing and evaporating the refrigerant. A drawback to this type of system and others like it is that they are quite bulky and awkward since they use large fluid pumps between the heat exchanger and the blanket or pad being heated or cooled. Some of the systems employ condensers, refrigerants and evaporator coils which are also bulky, awkward and of limited mobility.
It would therefore be advantageous to provide compact and economical devices for thermal treatment of maladies or trauma of the body provided with an efficient method of rapidly cooling/heating the refrigerant.